[time-nuts] strange hp 5345A option C19

[GandalfG8 at aol.com]

Hi Luca
 
I'm sorry to hear that, there's not much satisfaction in being right when  
it comes with such news attached:-(
 
The mod I devised was just a simple single link, totally reversible, that  
allowed testing, and use if required, of the counters without the internal  
reference.
It's been a while but if I remember rightly the link just routed  the 
external reference to feed both the internal and external inputs to the PLL  
which kept it locked and happy, but, of course, knowing that isn't really  of 
much help in this instance.
 
I may be able to help with some spares but will write to you directly about 
 that later, probably after the weekend, as I'm fiercely chasing my tail as 
 always and need to go out shortly anyway.
Time, or at least a very severe lack of it, is definitely driving me  even 
more nuts these days!
 
Regards
 
Nigel
GM8PZR
 
 
 
 
 
In a message dated 24/08/2013 10:29:10 GMT Daylight Time, iw2lje at gmail.com  
writes:

Hi  Nigel,
You are right.
A previous user, made a very  very bad fix!!!!
There are some traks modified in the PLL board related to  the external
reference.
Now I have to start with a complete restoration  process.
I have dismounted the counter and extracted the boards.  Fortunately
no other horrible items appeared.
Thank you  again.
Regards
Luca




Il giorno giovedì 22 agosto 2013,  ha scritto:

> Hi Luca
>
> The earlier 5345As were fitted  with the 10544A oscillator, I've seen 
units
> with both that and the  later 10811, so it could indeed be the original
> oscillator.
> If  your 10544A has the PCB edge connector and  is installed in the  usual
> place then without seeing what's actually been  done I'm a  bit lost as to
> why
> it would have been modified. If there was  a  problem perhaps with the
> original int/ext reference switching,  or with the phose  locking to an
> external
> source, that  might be a reason, but for that it sounds  like quite a
>  drastic
> fix:-)
>
> Regards
>
> Nigel
>  GM8PZR
>
>
> In a message dated 22/08/2013 10:31:06 GMT  Daylight Time, 
iw2lje at gmail.com<javascript:;>
>  writes:
>
> Thank  you Nigel for your comment.
> Now I  understand the reason why it may be  useful to have this
>  additional external link.
> In the counter is fitted  an oscillator  model 10544A (instead of a more
> known 10811), but I  think   that it is the original one because the
> date code of the serial   number is a bit old (year 1981). At that date,
> the 10544 was still in  use.  Observing carefully the way  in which the
> internal  connections to the  Ref In and Out are made, I notice that
> wires,  insulating material and  sockets are different from the original
>  HP's. So it seems actually to be a  user made modification not  related
> to option C19.
> Good  bye
>  Luca
>
>
>
>
> 2013/8/21    <GandalfG8 at aol.com>:
> > Hi Luca
> >
> >  There are other  items of HP equipment fitted with Ref Out  and Ref  In
> > terminals  joined by an external link, with the intention  that  the 
link
> is
> >  removed to connect an  external standard to the Ref In terminal,  but 
in
> a   "normal"
> > 5345A the external reference is used to phase  lock  the  internal
> oscillator
> > which means that the unit  can't work from an   external reference if 
the
> > internal  10MHz oscillator has been   removed.
> >
> >  However, I found some time ago that it is possible,  just by fitting  a
> > single link internally, to drive the counter via an   external reference
> even if
> > the internal standard has been  removed so  I'm guessing that the 
internal
> > standard on this  one might have been  removed at some time and a 
previous
> >  owner has fitted a non original  internal standard with a similar
>  provision  to
> > bypass the normal  arrangement.
>  >
> > It should be fairly easy to check just by looking  to  see if the
>  original
> > HP oscillator is still fitted  or whether  a different one has been
>  added.
>  >
> > Whether or not this  relates to the Option C19 I don't  know.
> >
> >  Regards
> >
> >  Nigel
> > GM8PZR
> >
> >
> > In a   message dated 21/08/2013 17:00:21 GMT Daylight Time,
>  iw2lje at gmail.com
> >  writes:
> >
> >  Dear  all,
> >
> > I have bought an HP  5345A.  It’s ok and I’m  very glad. On the rear
> > panel it is  wrote  "OPTION C19" (a little bit  strange!) and there are
>  > two  additional BNC installed on the little panel  normally  used to
> >  place the HPIB connector when present.
>  >
> > These 2 BNCs  are  named REF OUT and REF IN and  there is a jumper cable
> > that connects  the  output to  the input.
> >
> > It seems to be a modification  made  by some user  (very strange: I can’
t
> > understand why to  place  an extra auxiliary bypass  for the 10 MHz
> >   reference).
> >
> > Do you have an idea about this  strange   modification and about the
> > strange option  C19? Could it be a custom  option?  Could the option C19
>  > and the 2 BNC for the reference  be  related?
>  >
> > Thanks
> >
> > Bye
> >
>  >  Luca – IW2LJE – Milano –  Italy
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